1. Field of the Invention
The present invention relates to electronic components, such as surface acoustic wave devices and manufacturing methods thereof, and more particularly, to an electronic component having an improved configuration of an electrode pattern connected to an electronic component and a manufacturing method thereof.
2. Description of the Related Art
Recently, as a method of manufacturing many electronic components, such as surface acoustic wave filter devices, a method of preparing a wafer including a plurality of electronic components and dividing the wafer has been used. This method improves the mass productivity of electronic components.
When manufacturing electronic components, it is necessary to measure the characteristics of electronic components and determine whether the electronic components are non-defective components based on the measurement results. Alternatively, it is sometimes necessary to measure the characteristics of the electronic components for frequency adjustment performed at a subsequent stage. The measurement of characteristics of individual electronic components is complicated. It is therefore desirable to measure the characteristics of many electronic components before a wafer including these electronic components is divided. Japanese Unexamined Patent Application Publication No. 10-233642 discloses an example of a manufacturing method which enables the measurement of characteristics of many surface acoustic wave devices before a wafer including these surface acoustic wave devices is divided.
FIG. 11 is a schematic fragmentary plan view describing a manufacturing method disclosed in Japanese Unexamined Patent Application Publication No. 10-233642, that is, a method of measuring the characteristics of surface acoustic wave filter devices that are electronic components on a wafer. A lattice-like conductive pattern 502 is formed on a wafer 501. In a single rectangular region included in the lattice-like conductive pattern 502, an electrode configuration is provided so as to define a single surface acoustic wave device 503.
That is, on the wafer 501 defined by a piezoelectric substrate, the illustrated electrode configuration is provided in each of a plurality of rectangular regions included in the lattice-like conductive patterns 502, whereby a plurality of surface acoustic wave devices 503 are formed on the wafer 501.
As shown in FIG. 11, the surface acoustic wave device 503 is a ladder surface acoustic wave filter having a ladder circuit configuration in which a plurality of one-port SAW resonators 504 to 508 are electrically connected by conductive patterns. Among the one-port SAW resonators 504 to 508, the SAW resonators 504 and 508 which will eventually be connected to the ground potential are electrically connected to the lattice-like conductive pattern 502 using electrode patterns 509 and 510.
At the time of characteristic measurement, the input terminal of the surface acoustic wave device 503 is brought into contact with a hot probe and a ground probe, and the output terminal thereof is also brought into contact with the hot probe and the ground probe. In this case, the ground probe is brought into contact with the electrode pattern 509 on the side of the input terminal, and the ground probe is brought into contact with the electrode pattern 510 on the side of the output terminal. Subsequently, the characteristic measurement is performed.
To produce each of the plurality of surface acoustic wave devices 503, the wafer 501 is divided by cutting the wafer 501 along alternate long and short dash lines A and B after the above-described characteristic measurement has been performed.
In the manufacturing method disclosed in Japanese Unexamined Patent Application Publication No. 10-233642, at the time of manufacturing each of the plurality of surface acoustic wave devices 503, the wafer 501 is divided after the characteristic measurement has been performed. Accordingly, it can be easily determined whether each of the plurality of surface acoustic wave devices 503 is a non-defective component based on the measurement results. Furthermore, the mass productivity of the surface acoustic wave devices 503 is improved. In addition, in the measurement of a characteristic of each of the surface acoustic wave devices 503 formed on the wafer 501, a transmission characteristic that is almost the same as that of a finished product is obtained.
However, in a completed surface acoustic wave filter device, cut surfaces are provided along the alternate long and short dashed line A. In this case, the electrode patterns 509 and the 510 are partially cut, thereby being exposed on the cut surfaces.
Accordingly, moisture is likely to enter through the gaps between one side of the piezoelectric substrate that is the wafer and the cut surface of the electrode pattern 509 and between another side of the piezoelectric substrate and the cut surface of the electrode pattern 510. Electrode corrosion caused by moisture penetrates into the inside ends of the electrode patterns 509 and 510. In this case, an IDT included in a SAW resonator may corrode over time and the characteristic of the IDT may be deteriorated.
In particular, if the electrode patterns 509 and 510 or IDTs included in the surface acoustic wave device are made of an electrode material, such as Cu, that is susceptible to corrosion, corrosion is likely to occur over time.
In order to prevent such corrosion, a method of coating a cut line at the time of cutting of a wafer, that is, a dicing line, with a moisture-resistant resin may be used. However, even if the portions of the electrode patterns 509 and 510 to be cut are coated with the moisture-resistant resin, the cut surfaces of the electrode patterns 509 and 510 are exposed at the time of dicing. Accordingly, corrosion may occur over time. That is, if the above-described coating method is used, the time at which deterioration caused by corrosion occurs may be longer than the case in where the above-described coating method is not used. However, the characteristic deterioration may occur gradually over a long period of time.
The above-described corrosion occurs not only in surface acoustic wave devices, but also in various electronic components obtained by dividing a wafer including many electronic components. When the wafer is cut, an electrode pattern is exposed on the cut surface of the electronic component.